1,3-dimethyl-3-phenylbutyl acetate

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.4-D (Determination of the "Ready" Biodegradability - Manometric Respirometry Test)

GLP compliance:

yes (incl. QA statement)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge: aqueous phase of non-adapted activated sludge from municipal sewage treatment plant, 31137 Hildesheim, Germany treating mainly municipal sewage with hardly any industrial waste
- Pretreatment: The activated sludge was washed twice with chlorine-free tap water. The settled sludge was resuspended in mineral salts medium and maintained in an aerobic condition by aeration for 2 hours and 15 minutes and then homogenised with a blender. After sedimentation, the supernatant was decanted and maintained in an aerobic condition by aeration with CO2-free air for 6 days. 10 mL/L were used to initiate inoculation.
- Concentration of sludge: 10 mL/L were used to initiate inoculation.
- Initial cell/biomass concentration: 1.52 E+09 CFU/L

Duration of test (contact time):

28 d

Initial conc.:

20 mg/L

Based on:

test mat.

Initial conc.:

51.8 mg/L

Based on:

ThOD/L

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Composition of medium: Mineral salts medium according to OECD 301 F guideline
- Test temperature: nominal: 20 - 24, ± 1 °C; actual: 21.4 - 22.1 °C
- pH: 7.64 - 7.68 (test start), 7.51 - 7.84 (test end)
- pH adjusted: no
- Aeration of dilution water: continuous stirring
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: Brown glass bottles (volume 500 mL) containing 250 mL of test solution
- Number of culture flasks/concentration: 2 each for test item and inoculum control (blank control), 1 each for reference (functional) and toxicity control
- Method used to create aerobic conditions: aeration with CO2-free air for 6 days before inoculation.
- Measuring equipment: OxiTop® OC110 controller with OxiTop® measuring heads. A rubber sleeve with soda lime was hung into the opening of the bottles to absorb evolved CO2.

SAMPLING
- Sampling frequency: every 112 minutes (360 measuring points) during the 28 d test period
- Sampling method: direct measurement of oxygen concentration using OxiTop® measuring system

CONTROL AND BLANK SYSTEM
- Inoculum blank: inoculated mineral medium
- Functional/reference control: 45 mg/L sodium benzoate
- Toxicity control: 20 mg/L test Item and 45 mg/L reference Item (sodium benzoate)

STATISTICAL METHODS: Excel (Microsoft Corporation), SigmaPlot (SPSS Corporation).

Reference substance:

benzoic acid, sodium salt

Test performance:

The biodegradation in % was calculated based on the ThOD of 2.59 mg O2/mg test item.

Parameter:

% degradation (O2 consumption)

Value:

22

Sampling time:

28 d

Details on results:

The test item reached the 10 % level (beginning of biodegradation) within 5 days, however it did not reach the 60 % pass level by the end of the test. The mean biodegradation on day 28 was 22 %. The test item is therefore considered to be not readily biodegradable under the strict terms and conditions of OECD Guideline No. 301 F.

Results with reference substance:

The pass level for biodegradation (> 60 % degradation) was reached within 3 days, therefore the validity criterion that the degradation should be > 60 % after 14 days was fulfilled.

The mean oxygen depletion in the inoculum control was 9.9 mg O₂/L on day 28.

Table:Biodegradation [%] of the Test Item in Comparison to the Functional Control and Toxicity Control

		Biodegradation (%) Study Day (d)
	Replicate	7	14	21	28
Test item (20 mg/L)	1	13	21	25	27
	2	12	15	14	16
Reference (45 mg/L)	1	83	90	92	95
Toxic control 20 mg/L Test Item +45 mg/L Reference Item	1	54	58	61	66

 

Validity criteria fulfilled:

yes

Remarks:

The total O2 depletion in the inoculum control after 28 days < 60 mg/L (9.9 mg/L). pH 6.0 - 8.5 at end of test. Difference in replicates was < 20 % (actual 11 %) at end of test. Reference substance met validity test.

Interpretation of results:

not readily biodegradable

Conclusions:

The test item reached 22 % degradation after 28 days, and therefore is considered to be not readily biodegradable.

Executive summary:

The ready biodegradability of the test item was determined with non-adapted activated sludge for a period of 28 days in the test according to the OECD 301 F guideline. A blank control, functional (reference item) control and toxicity control were all included in the test set up. The validity criteria for the study were fulfilled. The study is considered to be suitable for use as the key study for this endpoint.

The test item reached 22 % degradation after 28 days, and therefore is considered to be not readily biodegradable. The results of the study also show that the test item is not inhibitory to sewage treatment microorganisms at tested concentration of 20 mg/L.

Description of key information

The test item is considered to be not readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Additional information

Two biodegradation studies are available for the test item showing that it is not readily biodegradable.

The biodegradability of the test item was tested with non-adapted activated sludge for a period of 28 days (2015). This study is GLP compliant and follows OECD guideline 301F. The study included a blank control, functional (reference item) control and toxicity control in the test set up. All validity criteria for the study were met. Therefore, it has been assigned a reliability score of 1 (reliable without restrictions). The test item reached 22 % degradation after 28 days, and therefore is considered to be not readily biodegradable.

 

In the second study (1996), the test item degraded by 15.5 % within 28 days and was therefore considered as not readily biodegradable. The study was non-GLP compliant and performed according to the guidance of German Environmental Agency (1990) (BODIS Test, similar to ISO 10708) and was assigned a reliability score of 2 (reliable with restrictions). Therefore, the study is considered to be suitable as a supporting study for this endpoint.